Figure 1: The biological interactions of Prochlorococcus with oxygen and light.
Bioptical Analysis of Growth Rates
Using a Multi-Cultivator, two strains of Prochlorococcus (MED4, MIT9313) were monitored for OD680 (Chlorophyll and scattering) and OD720 (cell scattering). Under 22°C, 12h photoperiod of blue light (450 ± 45 nm), and combinations of dissolved O2 (250, 25, 2 µM) and light levels (30, 90, 180 µmol photons m-2 s-1).
Bioptical Functional Measurements
Exposed samples under 250, 25, 2 µM O2, and a series of increasing light levels to track ‘light response’ curves of Photosystem II electron transport, using Solisense FRRf Instrument. Photosystem I and Photosystem II electron transport in parallel, using Dual-PAM-100 Instrument.
Figure 2: Light Response Curves of PSII electron transport (e- PSII-1 s-1) vs measurement light (µmol photons m-2 s-1) for Prochlorococcus strains MED4 and MIT9313, after growth under combinations of light level (rows, 30, 90, 180 µmol photons m-2 s-1) and oxygen concentration (columns, 2, 25, 250 µM). The curves were measured under 2 (red), 25 (green), or 250 (blue) µM O2. Lines show Platt curve fits.
Figure 3: Maximum PSII Electron Transport Rate (Pmax) for Prochlorococcus MED4 and MIT9313, derived from light response curve fits, vs. measurement oxygen concentrations (error bars = SE). Data is grouped by strain and growth oxygen concentration (columns), and by growth light levels (rows).
Figure 4: PSI electron transport (e- PSI-1 s-1) vs PSII electron transport (e- PSII-1 s-1) for Prochlorococcus strains MED4 and MIT9313 after growth under different combinations of light level (30, 90 µmol photons m-2 s-1) and oxygen concentration (2, 25, 250 µM). Mesurement under 2.5 (red), 25 (blue), or 250 (green) µM O2.